public class Main
{
    public static void main1(String[] args)
    {
        int a = 100;
        long b = 1900;
        System.out.println(a);
        System.out.println("Hello world!");
        System.out.println(b);
        boolean flg = true;
        System.out.println(flg);
        byte b1 = 125;
        byte b2 = 123;
        byte b3 = (byte) (b1 + b2);
        System.out.println(b1);
        System.out.println(b2);
        System.out.println(b3);
    }
    public static void main2(String[] args)//字符串拼接
    {
        String s1="好好学习";
        String s2="天天向上";
        System.out.println(s1+s2);
        System.out.println("===========");
        //调用Integer的方法来实现转换
        String s3="10009";
        int ret1=Integer.valueOf(s3);
        System.out.println(ret1);
        int ret2=Integer.parseInt(s3);
        System.out.println(ret2);

    }
    public static void main(String[] args)
    {
        System.out.println(5/2);
        System.out.println((float)5/2);
        System.out.println(5/(float)2);
        System.out.println((float)(5/2));
       // System.out.println(10/0);//会出现算数异常，除数不能是0
        System.out.println("===========");
        System.out.println(10%3);
        System.out.println(10%-3);
        System.out.println(-10%3);
        System.out.println(-10%-3);
        System.out.println(11.5%2);
        int a=10;
        int b=++a;//a=a+1  b=a
        //int b=a++;  b=a  b=a+1
        System.out.println(a);
        System.out.println(b);

    }//ctr+shift+/块注释
    //运算符会帮我们进行类型转换  c+=d就是c=(int)(c+d)


}
